Process for the production of carboxylic acid esters and/or carboxylic acids

ABSTRACT

Carboxylic acid esters are produced by reacting an unsaturated hydrocarbon, for example an olefin or an alkyne, with carbon monoxide and an alcohol in the presence of a protonic acid and as catalyst (a) at least one of the metals palladium, rhodium, ruthenium, iridium and cobalt, and (b) copper. In a modification of the invention carboxylic acids are produced by omitting the alcohol reactant and replacing it with water in an amount up to 8 mole equivalents based on the unsaturated hydrocarbon and a solvent other than an alochol, for example tetrahydrofuran.

The present invention relates in general to a process for the productionof carboxlyic acid esters and/or carboxylic acids and in particular to aprocess for the production of carboxylic acid esters and/or carboxylicacids by the catalysed reaction of an unsaturated hydrocarbon, carbonmonoxide and either water or an alcohol, optionally in the presence ofoxygen.

Processes for the production of esters by reacting an olefin with carbonmonoxide and an alcohol in the presence of a catalyst and in thepresence or absence of oxygen are known. Representative of the publishedart are U.S. Pat. No. 4,303,589, Belgian Pat. No. 877770, JapanesePatent Publication No. 53040709 and U.S. Pat. No. 3,780,074.

U.S. Pat. No. 4,303,589 (Monsanto) describes a process for theproduction of carboxylate esters by (a) reacting internal olefins withcarbon monoxide and an alcohol at 170° to 200° C. and 1200-1800 psig inthe presence of a cobalt catalyst and a pyridine promoter, (b) dilutingthe reaction mixture with a large amount of hydrocarbon to cause phaseseparation, (c) separating the ester from the other phase, whichcontains more than 90% of the cobalt catalyst and (d) recycling thecatalyst to step (a).

Belgian Pat. No. 877770 describes the production of polycarboxylicesters by reacting an olefin containing at least two conjugated doublebonds with carbon monoxide and an alcohol in the presence of a base anda palladium/copper catalyst.

Japanese Patent Publication No. 5 3040 709 describes the production ofdicarboxylic acid diesters by reacting an olefin, carbon monoxide,oxygen and an alcohol in the presence of a catalyst containing (a) apalladium group metal or a compound thereof, (b) a copper salt and (c) atertiary amine.

Finally, U.S. Pat. No. 3,780,074 describes the production of alkadienoicacid esters by reacting a 4-12 carbon acyclic conjugated aliphaticdiolefin with a 1 to 20 carbon monohydroxy alcohol and carbon monoxidein the presence of zero valent palladium and a phosphine activator at80° to 160° C. in the absence of oxygen.

Methods are also known for the hydroesterification of acetylene toproduce isomeric esters. For example, G. P. Chiusli et al report inChem. Ind., 977, (1968) the reaction of acetylene with carbon monoxidein the presence of 4% oxygen and thiourea and a palladium (II) chloridecatalyst. A disadvantage of this process is that the selectivity toisomeric esters (cis and trans-diesters) is considerably reduced by theaccompanying formation of polymeric materials and isomeric muconateesters.

We have now found that carboxylic acid esters and/or carboxylic acidscan be produced by reacting an unsaturated hydrocarbon with carbonmonoxide and either water or an alcohol in the presence of a protonicacid and as catalyst (a) at least one of the metals palladium, rhodium,ruthenium, iridium and cobalt, and (b) copper, both in the presence andthe absence of oxygen. In contrast with the majority of prior artprocesses which utilize a base as an essential reactant, the process ofthe present invention utilises an acid. The process of the invention incontrast with prior art processes can be operated under relatively mildconditions and exhibits a high regiospecificity to desirable products.

Accordingly, the present invention in one aspect provides a process forthe production of a carboxylic acid ester which process comprisesreacting an unsaturated hydrocarbon with carbon monoxide and an alcoholin the presence of a protonic acid and as catalyst (a) at least one ofthe metals palladium, rhodium, ruthenium, iridium and cobalt, and (b)copper.

The unsaturated hydrocarbon may suitably be an olfein. The olefin maysuitably be an acyclic olefin containing from 2 to 30 carbon atoms permolecule or a cyclic olefin containing from 5 to 30 carbon atoms permolecule. The olefin may have either 1, 2 or 3 olefinic carbon-carbondouble bonds per molecule, which double bonds may be internal orterminal and may be conjugated or non-conjugated in olefins containing aplurality of carbon-carbon double bonds. Suitable olefins may berepresented by the general formula RCH═CHR¹ wherein R and R¹ areindependently either hydrogen, alkyl, alkenyl, alkadienyl, cycloalkyl,aryl, alkaryl, cycloalkenyl or cycloalkadienyl groups, or R and R¹ takentogether form a cyclic system. Examples of suitable mono-olefins includepropylene, 1-butene, 2-butene, 1-pentene, 2-pentene, 1-hexene, 2-hexene,3-hexene, 1-octene, 1-decene, cyclododecene, 2-methyl-1-undecene,styrene, 4-methylstyrene, 4-isopropylstyrene, and the like. Examples ofsuitable diolefins include 1,3-butadiene, 1,3-pentadiene, 1,5-hexadiene,4-vinyl cyclohexene, 1,7-octadiene, 1,9-decadiene and the like.Alternatively the diolefin may be allene or an allene homologue, forexample dimethyl allene. Examples of suitable triolefins include1,5,9-cyclododecatriene, cycloheptatriene and the like. Mixtures ofolefins may also be employed. Terminal mono-olefins react to givebranched chain esters. Internal mono-olefins, for example 2-decene and4-methyl-2-pentene react exclusively at the 2-position, the cis-isomerbeing more reactive than the trans-isomer.

Alternatively, the unsaturated hydrocarbon may be an alkyne. The alkynemay be either a terminal or an internal alkyne. Suitable terminalalkynes include acetylene, 1-pentyne, 1-hexyne, 1-octyne,benzylacetylene, cyclohexylacetylene and 3-methyl-1-pentyne. Suitableinternal alkynes include 2-heptyne, 2-nonyne, 4-methyl-2-pentyne and2,9-dimethyl-5-decyne. Typically, using acetylene as the unsaturatedhydrocarbon the product principally comprises dimethyl maleate togetherwith a minor proportion of dimethyl furmarate. Generally, terminalalkynes give the cis-diester as the principal product and thetrans-diester as a by-product. Internal alkynes on the other handgenerally give monoesters, not diesters, and furthermore the monoesterstend to be of cis stereochemistry.

The carbon monoxide may be provided by any suitable source. The carbonmonoxide pressure may suitably be the autogenous pressure at thereaction temperature employed. Alternatively, elevated pressures,suitably in the range from 2 to 250 psig above the autogenous pressureat the reaction temperature may be employed.

As regards the alcohol reactant, monohydric and polyhydric alcohols maybe employed. Suitable alcohols may be represented by the formula R₂ CHOHwherein R is independently hydrogen, alkyl, aryl or hydroxyalkyl, or thetwo groups R together form a ring. Suitably the alcohol is an alkanol.Examples of suitable alcohols include methanol, ethanol, propanols,butanols, pentanols, hexanols, for example 2-ethylhexanol, benzylalcohol and 1,4-butanediol. The amount of alcohol employed may suitablybe at least the stoichiometric amount required to react with theunsaturated hydrocarbon. It is preferred, however, to employ asubstantial excess of alcohol over the stoichiometric amount, thealcohol then performing the dual role of reactant and diluent for thereaction.

The protonic acid may be either a mineral acid, preferably hydrochloricacid or sulphuric acid, or an organic acid which may suitably be acarboxylic acid.

With regard to the catalyst, one or more of the metals palladium,rhodium, ruthenium, iridium and cobalt is employed as component (a). Themetal(s) may be in the form of the elemental metal(s), such as a finelydivided powder, or in the form of a compound of the metal(s). Suitablecompounds of the metal(s) include the chlorides, iodides, acetates andnitrates, preferably the chlorides. Preferably the metal is palladium,suitably in the form of palladium (11) chloride.

Copper, which constitutes component (b) of the catalyst may suitably beadded as a cuprous or a cupric compound or as a mixture thereof. A widevariety of copper compounds may be used in the process of the invention.Examples of suitable copper compounds include copper (I) acetate, copper(11) acetylacetonate, copper (I) bromide, copper (I) chloride, copper(11) chloride, copper (I) iodide, copper (11) nitrate, and the like.

As regards the ratios of the catalyst components, the molar ratio ofcopper components (b) to metal(s) component (a) may suitably be in therange from 1:1 to 200:1, preferably from 2:1 to 60:1.

The molar ratio of unsaturated hydrocarbon to the metal(s) component (a)may suitably be in the range from 5:1 to 1000:1, preferably from 10:1 to250:1.

Oxygen may be present or absent. However, it is preferred to operate inthe presence of oxygen because by doing so the product yields can beimproved. Oxygen may be supplied to the reaction either as essentiallypure oxygen or admixed with other gases which are substantially inertunder the reaction conditions. Air may conveniently be used as thesource of oxygen. The oxygen pressure may suitably be the autogenouspressure at the reaction temperature employed. Alternatively elevatedpressures may be employed if desired.

A supplemental solvent may be employed if desired. The particularsolvent employed may form a single phase with the alcohol reactant.Alternatively a solvent which is capable of forming a second liquidphase may be employed. The particular solvent employed should be inertunder the reaction conditions. Suitable solvents which form a singlephase with the alcohol reactant include oxygenated hydrocarbons, forexample tetrahydrofuran. Suitable solvents capable of forming a secondliquid phase include aliphatic hydrocarbons, cycloaliphatichydrocarbons, aromatic hydrocarbons, alkyl-substituted aromatichydrocarbons or halogenated aliphatic or aromatic hydrocarbons. Examplesof suitable solvents capable of forming a second liquid phase includebenzene, toluene, hexane, cyclohexane, chlorobenzene, bromobenzene, axylene, dichloromethane, chloroform and 1,2-dichloroethane. It will beappreciated by those skilled in the art that the organic solvent shouldbe chosen having regard to the difference in boiling points between theproducts of the reaction and the solvent so as to facilitate separationof the reaction mixture into its individual components. The amount ofsupplemental solvent based on the olefin reactant may vary over a widerange, suitably from 20 to 0.2, preferably from 5 to 1, volumes ofsupplemental solvent per volume of olefin reactant.

If, in a modification of the invention, the alcohol reactant is replacedby water, provided that the amount of water is less than 8 moleequivalents based on the unsaturated hydrocarbon reactant and a solventother than an alcohol is employed, then instead of carboxylic acidester, there is formed the corresponding carboxylic acid.

Preferably the amount of water employed is less than 5, even morepreferably about 1 mole equivalent based on the unsaturated hydrocarbonreactant.

Any suitable solvent other than an alcohol may be employed. Suitablesolvents include ethers and hydrocarbons, for example paraffinic andaromatic hydrocarbons. Preferably the solvent is an ether. Examples ofsuitable ethers include tetrahydrofuran, dioxan, glymes and the crownethers, of which tetrahydrofuran is preferred.

The process may suitably be operated at ambient temperature, thoughelevated temperatures, for example in the range 20° to 150° C. or evenhigher may be employed. The reaction time may vary over a wide range,suitably from about 30 minutes to 8 hours, though longer reaction timesmay be employed if desired.

The process may be carried out batchwise or continuously, preferablycontinuously.

The invention will now be described in greater detail by reference tothe following Examples.

PROCESS OPERATED IN THE PRESENCE OF OXYGEN EXAMPLE 1

Palladium (11) chloride (0.1 g; 0.56 mmol) was added to methanol (50 ml)through which was bubbled carbon monoxide (1 atmosphere). After 1 minuteconc. hydrochloric acid (0.5 ml) was added. When the solution turnedyellow (indicating that the palladium chloride had dissolved), copper(11) chloride (0.5 g; 3.7 mmol) was added and oxygen (1 atmosphere) wasbubbled through the solution in addition to the carbon monoxide.1-Decene (6 mmol) was then added and the reaction mixture was stirredfor 4 hours at 25° C. After 2 hours a further 0.5 ml conc. hydrochloricacid was added.

The reaction product was then extracted with hexane and the hexaneevaporated to give a pure product which was identified as methyl2-methyl decanoate. The ester was obtained in 100% yield based on olefinreactant.

EXAMPLE 2

Example 1 was repeated except that 1-decene was replaced by1,7-octadiene.

EXAMPLE 3

Example 1 was repeated except that 1-decene was replaced by1,9-decadiene and the reaction time was reduced to 3 hours.

EXAMPLE 4

Example 1 was repeated except that 1-decene was replaced bycyclododecene.

EXAMPLE 5

Example 1 was repeated except that 1-decene was replaced by propene.

EXAMPLE 6

Example 1 was repeated except that 1-decene was replaced by2-methyl-1-undecene and the product was separated by distillation afterextraction with hexane.

EXAMPLE 7

Example 6 was repeated except that 2-methyl-1-undecene was replaced by4-methylstyrene.

The results of Examples 2 to 7 together with those of Example 1 aregiven in Table 1.

EXAMPLE 8

Example 1 was repeated except that the conc. hydrochloric acid wasreplaced by conc. sulphuric acid (0.33 g).

Methyl 2-methyl decanoate was obtained in 92% yield.

EXAMPLE 9

The procedure of Example 1 was repeated except that instead of methanolthere was used 1,4-butane diol (0.7 g) and tetrahydrofuran (30 ml) wasused as a supplemental solvent. The amounts of other reactants were asfollows:

palladium (II) chloride=0.7 mmol

copper (II) chloride=6 mmol

conc. hydrochloric acid=0.1 ml

1-decene=1.09 g

The carbon monoxide/oxygen was bubbled through the mixture for 16 hours.

After distillation of the crude product, the pure monoester of formula##STR1## was obtained in 50% yield.

EXAMPLE 10

Palladium (11) chloride (0.1 g; 0.56 mmol) was added to methanol (50 ml)through which was bubbled carbon monoxide (1 atmosphere). After 1 minuteconc. hydrochloric acid (0.5 ml) was added. When the solution turnedyellow (indicating that the palladium chloride had dissolved), copper(11) chloride (0.5 g; 3.7 mmol) was added and oxygen (1 atmosphere) wasbubbled through the solution in addition to the carbon monoxide.Acetylene (6 mmol) was then bubbled through the solution for 4 hours at25° C. After 2 hours a further 0.5 ml conc. hydrochloric acid was added.

The reaction product was then extracted with hexane and the hexaneevaporated. Analysis of the product give dimethyl maleate (86% yield)and dimethyl fumarate (14% yield).

EXAMPLE 11

The procedure of Example 1 was repeated except that acetylene wasreplaced by 1-pentyne. Cis- and trans-C₃ H₇ C(COOCH₃)═CHCOOCH₃ wereobtained in 72 and 25% yield respectively.

EXAMPLE 12

The procedure of Example 10 was repeated except that acetylene wasreplaced by 1-hexyne. Cis- and trans-C₄ H₉ C(COOCH₃)═CHCOOCH₃ wereobtained in 76 and 24% yield respectively.

EXAMPLE 13

The procedure of Example 10 was repeated except that acetylene wasreplaced by 1-octyne. Cis- and trans-C₆ H₁₃ C(COOCH₃)═CHCOOCH₃ wereobtained in 80 and 20% respectively.

EXAMPLE 14

The procedure of Example 10 was repeated except that acetylene wasreplaced by benzyl acetylene. Cis- and trans-PhCH₂ CH₂C(COOCH₃)═CHCOOCH₃ were obtained in 74 and 26% yield respectively

EXAMPLE 15

The procedure of Example 10 was repeated except that acetylene wasreplaced by cyclohexylacetylene. Cis- and trans-C₆ H₁₁C(COOCH₃)═CHCOOCH₃ were obtained in 85 and 15% yield respectively.

EXAMPLE 16

The procedure of Example 10 was repeated except that acetylene wasreplaced by 3-methyl-1-pentyne. Cis- and trans-C₂ H₅CH(CH₃)C(COOCH₃)═CHCOOCH₃ were obtained in 84 and 16% yieldrespectively.

EXAMPLE 17

The procedure of Example 10 was repeated except that acetylene wasreplaced by 2-heptyne. CH₃ (CH₂)₃ CH═C(CH₃)COOCH₃ and an ether wereobtained in 90 and 10% yield respectively.

EXAMPLE 18

The procedure of Example 10 was repeated except that acetylene wasreplaced by 2-nonyne.

CH₃ (CH₂)₅ CH═C(CH₃)COOCH₃ and an ether were obtained in a ratio of 60and 40% yield respectively.

EXAMPLE 19

The procedure of Example 10 was repeated except that acetylene wasreplaced by 4-methyl-2-pentyne. (CH₃)₂ CHCH═C(CH₃)COOCH₃ and an etherwere obtained in 75 and 25% yield respectively.

EXAMPLE 20

The procedure of Example 10 was repeated except that acetylene wasreplaced by 2,9-dimethyl-5-decyne. Cis-(CH₃)₂ CHCH₂ CH₂ CH═C(CH₂ CH₂CH[CH₃ ]₂)COOCH₃ and an ether were obtained in 70 and 30% yieldrespectively.

EXAMPLE 21

Example 15 was repeated except that methanol was replaced by ethanol.Cis- and trans-C₆ H₁₁ C(COOC₂ H₅)═CHCOOC₂ H₅ were obtained in 86 and 13%yield respectively.

EXAMPLE 22

Example 17 was repeated except that n-propyl alcohol was used in placeof methanol.

Cis-CH₃ (CH₂)₃ CH═C(CH₃)COOC₃ H₇ was obtained in 76% yield.

In Examples 10 to 22 the % yields are based on reactant alkyne.

EXAMPLE 23

Carbon monoxide was bubbled through a solution containingtetrahydrofuran (30 ml) and water (1 ml). Palladium (II) chloride (0.140g, 0.78 mmol) was added, followed by concentrated hydrochloric acid (1.0ml), copper (II) chloride (0.84 g, 6.24 mmol), and then oxygen wasbubbled through the mixture. 1-Decene (7.8 mmol) was added and thereaction mixture was stirred at room temperature for 4 hours.

The product was worked-up by adding distilled water (50 ml) andextracting three times with hexane (in total 250 ml). The extract wasdried using magnesium sulphate and then concentrated. Furtherpurification was carried out by dissolving the acid in 1M NaOH,extracting with ether, acidifying, and extracting again with ether.

2-Methyldecanoic acid was obtained in 100% yield.

EXAMPLE 24

The procedure of Example 23 was repeated except that 1-decene wasreplaced by 1-octene and the reaction time was increased to 18 hours.

2-Methyloctanoic acid was obtained in 92% yield.

EXAMPLE 25

The procedure of Example 23 was repeated except that 1-decene wasreplaced by vinylcyclohexene.

C₆ H₁₁ CH(CH₃)COOH was obtained in 53% yield.

EXAMPLE 26

The procedure of Example 25 was repeated except that the reaction timewas increased to 18 hours.

C₆ H₁₁ CH(CH₃)COOH was obtained in 89% yield.

EXAMPLE 27

The procedure of Example 23 was repeated except that 1-decene wasreplaced by 1,7-octadiene and the reaction time was increased to 18hours.

HOCOCH(CH₃)(CH₂)₄ CH(CH₃)COOH was obtained in 93% yield.

EXAMPLE 28

The procedure of Example 23 was repeated except that 1-decene wasreplaced by 1,9-decadiene and the reaction time was increased to 18hours.

HOCOCH(CH₃)(CH₂)₆ CH(CH₃)COOH was obtained in 100% yield.

EXAMPLE 29

The procedure of Example 23 was repeated except that 1-decene wasreplaced by cis-2-decene.

CH₃ (CH₂)₇ CH(CH₃)COOH was obtained in 59% yield.

EXAMPLE 30

The procedure of Example 23 was repeated except that 1-decene wasreplaced by trans-2-decene.

CH₃ (CH₂)₇ CH(CH₃)COOH was obtained in 30% yield.

EXAMPLE 31

The procedure of Example 30 was repeated except that the time wasincreased to 18 hours.

CH₃ (CH₂)₇ CH(CH₃)COOH was obtained in 77% yield.

EXAMPLE 32

The procedure of Example 23 was repeated except that cyclododecene wasused instead of 1-decene. The yield of cyclododecanecarboxylic acid was64%.

EXAMPLE 33

The procedure of Example 23 was repeated except thatcis-4-methyl-2-pentene was used instead of 1-decene. The yield of2,4-dimethylpentanoic acid was 84%.

EXAMPLE 34

The procedure of Example 23 was repeated except thattrans-4-methyl-2-pentene was used instead of 1-decene. The yield of2,4-dimethylpentanoic acid was 64%.

EXAMPLE 35

The procedure of Example 23 was used except that instead of 1-decenethere was used 1,7-octadiene (1.15 ml; 7.8 mmol). The amounts of theother reactants were as follows:

Tetrahydrofuran=30 ml

Palladium (II) chloride=0.130 g (0.7 mmol)

Conc. hydrochloric acid=0.1 ml

Copper (II) chloride=6 mmol.

Water=0.14 ml (7.8 mmole)

Carbon monoxide/oxygen was bubbled through the mixture for 16 hours.

An 80% mixture of the monoacids of formula:

    CH.sub.3 CH(COOH)(CH.sub.2).sub.4 CH═CH.sub.2

and

    CH.sub.3 CH(COOH)(CH.sub.2).sub.3 CH═CH.sub.2 CH.sub.3

were obtained.

PROCESS OPERATED IN THE ABSENCE OF OXYGEN EXAMPLE 36

Palladium (11) chloride (0.1 g; 0.56 mmol) was added to methanol (50 ml)through which was bubbled carbon monoxide (1 atmosphere). After 1 mconc. hydrochloric acid (1.0 ml) was added. The solution turned yellow.1-Decene (6 mmol) was added and the reaction mixture was stirred at roomtemperature. When the reaction mixture turned green, a small amount ofcopper (11) chloride was added [1:1 ratio overall of palladium (11)chloride to copper (11) chloride]. This operation was repeated as longas the solution turned green. Eventually the solution remained yellow,at which point it was extracted with hexane. The hexane was thenevaporated to give methyl 2-methyl decanoate in 100% yield.

                  TABLE 1                                                         ______________________________________                                        EX-                                                                           AM-                                 YIELD                                     PLE  OLEFIN     PRODUCT             (%)                                       ______________________________________                                        1    1-decene                                                                                  ##STR2##           100                                       2    1,7-octadiene                                                                             ##STR3##           100                                       3    1,9-decadiene                                                                             ##STR4##           70                                        4    cyclo-     methyl cyclododecane                                                                              85                                             dodecene   carboxylate                                                   5    propene    (CH.sub.3).sub.2 CHCOOCH.sub.3                                                                    100*                                      6    2-methyl-1-                                                                              C.sub.9 H.sub.19 C(CH.sub.3).sub.2 COOCH.sub.3                                                    63                                             undecene   C.sub.9 H.sub.19 C(CH.sub.3).sub.2 OCH.sub.3                                                      18                                                        Internal olefin      8                                        7    4-methyl- styrene                                                                         ##STR5##           90                                                         ##STR6##            8                                                        Internal olefin      2                                        ______________________________________                                         *The yield is approximate since the exact weight of propene was not           determined. No CH.sub.3 CH.sub.2 CH.sub.2 COOCH.sub.3 was isolated.      

EXAMPLE 37

Example 36 was repeated except that 1-decene was replaced by 1-pentene.

EXAMPLE 38

Example 36 was repeated except that 1-decene was replaced by2-methyl-1-undecene and the product was separated by distillation afterextraction with hexane.

EXAMPLE 39

Example 36 was repeated except that 1-decene was replaced by4-methylstyrene and the product was separated by distillation afterextraction with hexane.

The results of Examples 36 to 39, together with those for Example 36,are given in Table 2.

In Examples 23 to 39 the % yields are based on reactant olefin.

                  TABLE 2                                                         ______________________________________                                        EXAM-                           YIELD                                         PLE    OLEFIN                   (%)                                           ______________________________________                                        36     1-decene                                                                                   ##STR7##        100                                       37     1-pentene                                                                                  ##STR8##         90                                       38     2-methyl-1- C.sub.9 H.sub.19 C(CH.sub.3).sub.2 COOCH.sub.3                                                  6                                               undecene    C.sub.9 H.sub.19 C(CH.sub.3).sub.2 OCH.sub.3                                                    14                                       39     4-methylstyrene                                                                            ##STR9##         50                                                           ##STR10##        50 50                                    ______________________________________                                    

We claim:
 1. A process for the production from an olefinicallyunsaturated hydrocarbon of a branched-chain saturated carboxylic acidester and/or the corresponding carboxylic acid wherein the number ofester or carboxylic acid groups is equal to the number of olefinicdouble bonds in the olefinically unsaturated hydrocarbon which processcomprises reacting the olefinically unsaturated hydrocarbon with carbonmonoxide and either alcohol or water respectively in the presence ofoxygen,of an added protonic acid selected from the group consisting ofhydrochloric acid, sulphuric acid and an organic acid, and as catalyst(a) palladium, and (b) copper, the component (a) being in the form of anelemental metal or a compound thereof, and the component (b) being inthe form of a compound thereof.
 2. A process according to claim 1wherein the alcohol has the formula R₂ CHOH wherein R is independentlyhydrogen, alkyl, aryl or hydroxalkyl, or the two groups R together forma ring.
 3. A process according to claim 1 wherein the olefinicallyunsaturated hydrocarbon is reacted with carbon monoxide and water,provided that the amount of water is less than 8 mole equivalents basedon the olefinically unsaturated hydrocarbon, in the presence of asolvent other than an alcohol and the product produced thereby is thecarboxylic acid.
 4. A process according to claim 3 wherein the solventis an ether.
 5. A process according to claim 1 wherein the reaction iscarried out at a temperature in the range 20° to 150° C.
 6. A processfor the production of an unsaturated carboxylic acid di-ester and/or thecorresponding dicarboxylic acid which process comprises reacting anacetylenically unsaturated hydrocarbon with carbon monoxide and eitheralcohol or water respectively in the presence of oxygen,a protonic acidselected from the group consisting of hydrochloric acid, sulphuric acid,and an organic acid, and as catalyst (a) palladium, and (b) copper, thecomponent (a) being in the form of elemental metal or a compoundthereof, and the component (b) being in the form of a compound thereof.7. A process according to claim 6 wherein the alcohol has the formula R₂CHOH wherein R is independently hydrogen, alkyl, aryl or hydroxalkyl, orthe two groups R together form a ring.
 8. A process according to claim 6wherein the acetylenically unsaturated hydrocarbon is reacted withcarbon monoxide and water, provided that the amount of water is lessthan 8 mole equivalents based on the acetylenically unsaturatedhydrocarbon, in the presence of a solvent other than an alcohol and theproduct produced thereby is the carboxylic acid.
 9. A process accordingto claim 8 wherein the solvent is an ether.
 10. A process according toclaim 6 wherein the reaction is carried out at a temperature in therange 20° to 150° C.
 11. A process for the production, from an acyclicolefinically unsaturated hydrocarbon of 2 carbon atoms, of a saturatedcarboxylic acid ester and/or the corresponding carboxylic acid whereinthe number of ester or carboxylic acid groups is equal to the number ofolefinic double bonds in the olefinically unsaturated hydrocarbon whichprocess comprises reacting the acyclic olefinically unsaturatedhydrocarbon of 2 carbon atoms with carbon monoxide and either alcohol orwater respectively in the presence of oxygen,of an added protonic acidselected from the group consisting of hydrochloric acid, sulphuric acidand an organic acid, as catalyst (a) palladium, and (b) copper, thecomponent (a) being in the form of an elemental metal or a compoundthereof, and the component (b) being in the form of a compound thereof.